Propeller



P. I.Y GRIFFIN'.

PROPELLER. I APPLICATION FILED IAN. III 1919. 1,360,933. I Patented Nov. 30, 1920.

n .Ei/9.1; 3.

.mounted While not limited thereto, myV rinvention is more particularly adapted for PATENT OFFICE.

PATRICK J'. GRIFFILL; 0F :DQRCHES'LEB',Y MASSACHUSETTS.

PROPELLER.

Specication of Letters Patent. Patented N0V 30, 1920.

Application filed January 11, 1919. Serial No. 270,713.

To all whom t ma camera:

' Be it known that PATRICK J. GRIFFIN, a citizen of the United States, and a resident of AVDorchester, in the county of Y Suolk, State of Massachusetts,` have invented an Improvement in Propellers, of which the following description, in connection with the accompanying drawings, is a specification,

like characters on the drawings representing like parts.

This invention relates to propellers which are'adapted by rotation in a iiuid medium to advance the structure on which they are use onv airplanes and similar craft wherein the propeller works in air.

-My invention will best be understood by reference -to the following description of an illustrative embodiment thereof ltaken in connection with the accompanying drawings wherein y Figure 1 is a side elevation of an'airplane propeller constructed in accordance with my invention;

Fig. 2 vis an end view thereof; and

Figs. 3 and 4 are sections on the lines 3 3 and 4-4, respectively, of Fig. Y1.

For convenience in the followingrdescription, I shall refer specifically to thepropeller as one for use on aircra j Referring to Fig. 1 of the drawings, I have there shown asV an example of my invention a propeller of composite structure, although my invention is not limited thereto. In such a composite propeller I may utilize as a part thereof a wooden propeller 5 of the type now commonly utilized on airplanes and embodying such features of form and proportion as have been empirically determined to be most eiicient. Such a propeller embodies a hub 7 secured in desired manner -on the shaft 9, from which hub radiate blades v11, usually 4.lenticular in sec# tion as shown in Fig. 3, and usually two in number as shown. The proportions, form and pitch of such a propeller have been determined by practice Vand I may follow the usual custom in these points. Conveniently,

however, the propeller 5 may be smaller thanv a propeller of the'usual type adapted to de- Vvelop a similar thrust for reasons which will hereinafter appear. Y In accordance with my invention I utilize auxiliary blades, as 13. which are hubless suitably varied. y In the present embodiment of my invention I have shown two sets of auxiliary blades 13 and 15, one set on each side of the main blades, but for the present I will confine my description tothe blades 13 since but one setof blades may be used, although I prefer` to use two sets, as shown inthe drawings. The blades 13 may be conveniently formed of v'metal of substantially uniform thickness and are disposed substantially parallel to the adjacent surface of the blade 11. The blade 13 is simil iar in form to the outer portion of the blade 11 but differs therefromin having no hub and'conveniently may be made to project beyond the tip of the mainblade, as indicated in Fig. 2. therwise described,l it may be said that the auxiliary blade 13 has throughout its surface substantially the same angle or pitch, which is that of the outeror most effective portion of the main blade 11, and, being hubless, need have no portion corresponding to the less effective inner portion of the main blade. w Y

The auxiliary blade 13 Vmay be supported in position relatively to the blade 11 byfany suitable means, but preferably by supports 17 which may be of stream line form as shown inFig. 4; and which are -desirably 'composite propeller shown for purposes of illustration I have disclosed bands 19 shrunk about the blades 11 and conveniently pinned thereto at 21 to resist separation by the centrifugal force of the rotating propeller. The supports 17, which are conveniently of metal, may be secured to the bands 19 by welding,

Vbrazing or some Asimilar process and are integral or integrally connected with the blades 13.

To resist the pull of centrifugal force on the blades 13, they may be stayed to the propeller shaft 9 at their inner ends and herein l show means providing for mutual support of the blades comprising a relatively sina1 connecting stay 23 between their inner ends which may be apertured, as indicated in `Fig; 2, to receive the propeller shaft, which af fords the stay a support. lt will be understood, however, that the connecting stay 23 is not similar to and does not correspond to the hub 7 to which the main blades are secured but that the auxiliary blades are supported primarily from the main blades 1l. rlhe blades 15 are disposed on the opposite side of the main blades 11 in a similar manner, preferably symmetrically to the blades 13thus providing a desirably balanced structure. Conveniently the auxiliary blades may be dished, as indicated in Fig. 3, thedishing being suoli as to present the concavesides forwardly of the normal direction. of rotation, herein rearwardly since the drawings are assumed to represent a tractor screw.

, Asbest indicated in Fig-2 and in Fig, 3, wherein the axial line is horizontal, the bladesof each set are preferably offset ai;- ially or staggered or echeloned. Thus, view* ing F ig. 2, in the counterclockwise rotation of the propeller the blades do not come to a given angular position and enter the air simultaneously but one after the other, and preferably this staggering is so arranged that the hindermost blade inthe direction of travel of the structure on which the propeller is mounted, herein the blade 15, will be angularly in advance of the relatively leading blade 11 which in turn is in advance of the blade 13. By the staggering of the blades the plurality of Vblades operates simultaneously on a larger area than any single blade, as willbe clearly understood from reference to Fig. 2; and by the preferable arrangement of this staggering as described, each blade as itjrotates enters air which is less disturbed from the action of the relatively leading blade than would otherwise be the case.

,A prime advantage of a propeller constructed in accordance with my invention lies in the increase of effective surface without corrseponding increase in effective surface'leading to difficulties in construction and in operation. lt has been demonstrated that the outer portion of a propeller adjai cent the tips of the blades does the major part of the work. The inner portion adjacent the hub is ineffective and it, together' with the hub, in fact constitutes a dran' on the mechanism.- Adjacent the axis ol' the propeller there is a dead body of air which retards the motion of the aircraft and through which the large hub of the propeller must be dragged. By the use of the auxiliary, hubless blades, as described, the area adjacent the outer circumference of the propeller is marlredly increased without correspoinling increase at the hub. Thus, the `driving power is greater while the retarding effect is the same. 1n a simple propeller the same increase in surface could not be obtained from an increase in the size of the blades 1l without a corresponding in* crease in the size of the inner parts, with a marked increase in weight and the -introduction of many construotional difficulties. 'Careful 'tests with a propeller constructed in accordance with my invention have indicated that it isof greater efficiency than ordinary Vpropellers with a single set of blades, in that there is less slip and the propeller better grips the air. However, disregarding this increase in efficiency, it will be apparent that if the same power were to be developed, my propeller might be made smaller in overall dimensions and could rotate at a slower rate, since the working surface is greater. Terrific strains are at present imposed on airplane propellers due to their great size and excessive speed and as the length of the blade is increased the linear speed of the parts rapidly increases and the propeller-s tend to tear themselves to pieces. The possibility of increasing the effective area of the blades without undue increase in the speed thereof and with anV additional limitation of speed, both linear and rotative, eliminates many structural difficulties presented iby the present type of propeller when designed to develop great power.

l have stated that careful tests appear to show a greater efficiency in a propeller of the type herein disclosed in that it obtains a better grip upon the air and has less slip. l state this as an empirical fact andfdo not wish to be bound to any particular theory as to the action. lt seems probable, however, that the following statements are correct. It has been shown in connection with lifting surfaces on airplanes that the same lifting power can be obtained from superposed planes as can be obtained from a larger single plane and with less friction provided the planes are made suitably nar row. A similar absence of retarding friction is probably present in my propeller. 1n biplanes it is stated that there is aV disadvantage in interference between the currents of air between the upper and lower planes, but it is my belief that in a propellerr as shown this interference, if it exists, is not a disadvantage but permits a more effective grip of each rotating blade upon the air. Referring vto Fig. l, it will be noted that a portion of the blade 13 acts against the body of air confined on either side by the segmental supports 17. lt is my belief that this insures a better grip of the blades upon the air.

The supports 17, however, have an additional function in that while they offer little substantial resistance to the regular rotation of the propeller .onv account Vof their lying in the circular orbit through; which the blades rotate, they do resistV side-slip and nose-dive as theyhave comparatively broad surfaces which are lmoved laterally through the air if the vehicle swerves.

Having thus described in detail a single preferred embodiment of my invention, the' principles illustrated thereby which I consider new and desire to secure by Letters Patent I shall express in the the following claims Y Y Y l. In a screw propeller a hub having a plurality of radiating blades and auxiliary hubless blades carried by said first blades in spaced relation thereto.

2. Ina screw propeller a hub having a plurality of radiating blades and auxiliary hubless blades carried by said first blades in spaced relation thereto, the auxiliary blades being similar in form and substantially parallel to the adjacent surfaces of the main blades. j

3. In a screw propeller a hub having a plurality of radiating blades and auxiliary hubless blades carried by said iirst blades in spaced relation thereto, the auxiliary blades being similar in form and substantially parallel to the adjacent surfaces of the main blades but offset relatively thereto axially of the propeller. l s

l. In a screw propeller a hub having a plurality of radiating blades and auxiliary blades similar in form to the outer portions of the main blades and homologously supported thereby in spaced relation thereto.

In a screw propeller a hub having a plurality of radiating` blades and auxiliary blades similar in form to the outer portions ofthe main blades and homologously supported thereby in spaced relation thereto, said auxiliary blades extending radially beyond the main blades.

6. In combination, a propeller shaft, a blade-carrying hub mounted rigidly thereon, and a plurality of blades of which some are integral with or rigidly mounted on said hub 'and others are rigidly atxed to said first-named blades and not attached to said hub. j Y f 7. The combination o f a hub and a screw propeller blade extending therefrom 1n a plane substantially at right Aangles to the axis of the propeller shaft and ending at its tip in such angle as is best adapted to secure the most effective grip upon the element in Y which the propellerturns, and an auxiliary blade fixedly secured on said first-named blade and having throughout its length sul stantially the same angle of inclination to the axis of rotation as the tip ofv said firstnamed blade. Y

8. In a screw propeller a hub having a axis of rotation.

9. In a screwf propeller a hub having radiating blades, auxiliary hubless blades and means for supporting each auxiliary blade in spaced, substantially parallel relation to a main blade comprising a pair of connecting supports in the form of cylindrical segments centered on the axis of rotation.

10. In a screw propeller a hub having a plurality of radiating blades, auxiliary hubless blades xedly supported beside the outer portions of the main blades, the supporting means comprising connecting supports in the form of cylindrical segments centered on the axis of rotation and disposed inwardly of the tips of the blades.

11. A screw propeller comprising radiating sets of homologous blades, the elements of each set being serially disposed in the direction of travel of the driven structure and relatively offset axially, each followingV blade being, in the normal rotative sense, in advance of the relatively leading blade.

12. A screw propeller having a main blade' and an auxiliary blade carried thereby in spaced relation thereto, extending outwardly beyond the tip of the main blade and terminating inwardly at such distance from said shaft that it does not extend into the area of disturbance in which little or no propulsive effect is gained.

13. A propeller having a hub, a main blade projecting therefrom, an auxiliary blade similar to the outer portion of the main blade and supported therebyV in spaced relation thereto and means to stay the auxiliary blade to the propeller shaft against centrifugal pull.

14. A propeller having a hub, a pair of blades projecting therefrom, auxiliary blades similar to the out-er portions of the main bladesV supported thereby in spaced relation thereto and a connecting stay between the inner ends of the auxiliary blades.

15.` A propeller having a hub, a pair of blades projecting therefrom, auxiliary blades similar to the outer` portions of the main blades supported thereby in spaced relation thereto and a connecting stay between the blades supported by the main blades 1'01'- Wzu'd and back of the same in xed relation thereto. Y

18. A. Screwy propelle having a hub with projecting blades and hubless auxiliary blades supported by tbe main blades forward and beek vof the same in fixed relation on the axis of rotation. l0

In testimony whereof have signed my name to tbls speelfeetlon.

PATRICK J. GMFFIN. 

